Washington: A US university students' project has stumbled upon figures that China could have 3,000 nuclear warheads, many times larger than the well established estimates of arms-control experts, sounding alarm bells in Pentagon.

Goergetown University students logging into sources as disparate as Google Earth, blogs and military journals have come out with an exhaustive research report claiming that the Chinese have built a vast network of secret underground tunnels to hide a sophisticated missile and nuclear arsenal.

Calling it "Underground Great Wall", the students pushed on by their hard charging professor, a former top Penatgon official, have said in the report that China could have as many as 3,000 nuclear warheads, far higher than the current estimates which range from 80 to 400, Washington Post reported.

The 363-page study, which according to the Post has not been published yet has claimed that Chinese Second Artillery Corps- designated to handle nuclear weapons- has dug thousands of miles of tunnels across the country to disperse the nukes and keep them away from prying eyes in the sky.

The study is yet to be released, but Washington Post said it has already sparked a Congressional hearing and been circulated among top officials in the Pentagon including the Air Force Vice-Chief of Staff.

The students' professor, Philip Karber, 65 spent the Cold War as a top strategist reporting directly to the Secretary of Defence and the Chairman of the Joint Chiefs of Staff, the paper said.

US official could not be reached to comment on the report, Washington Post said.